Bond-bending Forces Research Articles

Different rheological behaviors of reinforced poly(methylvinylsiloxane) by mesoporous and spherical silica microparticles

To elucidate the mechanism underlying the high performance of mesoporous silica aerogel microparticle (SAG) in reinforcing polymers, the hydrodynamic effect and reinforcement effect of SAG microparticle in Poly-methylvinylsiloxane (PMVS) were investigated. For comparison, regular spherical silica particles (SS) with a comparable particle size and smooth surface were also incorporated into the study as a contrasting filler. It was found that SAG tended to form aggregates with high aspect ratio (shape factor f values between 16-20) and highly branched backbone structures (x = 1.95). However, these aggregates are more loosely packed (df = 1.7) and easily break into smaller flocs under the influence of shear forces. The load-bearing mechanism of the spatial network formed by these aggregates as nodes was akin to physical gels controlled by bond-bending forces (BBFs), with a scaling exponent of G*r with φe-φc of ν = 3.84, close to the theoretical value of the BBFs model. In contrast, the SS particles formed more compact aggregates (f value approximately 1.6) in PMVS, with load-bearing characteristics of the spatial network formed by them closer to chemical gels controlled by central forces (CFs). The scaling exponent of G*r with φe-φc for SS/PMVS was found to be ν = 2.15, close to the theoretical value of the CFs model.

Computational study of lattice dynamics and mechanical properties of AlxIn1-xPySbzAs1-y-z/InP under the effect of composition

For the first time, the composition dependence of pentanary AlInPSbAs alloy is described. The effect of composition on the polarity (∝p), mechanical parameters have been calculated for the AlxIn1-xPySbzAs1-y-z alloy. The impact of composition on the internal strain parameter (ζ), bond-bending force constant (α), bond-stretching force constant (β), and sound velocity (v) has been reported. Results from experiments and the investigated properties of the new alloy show a high degree of agreement. In this work, the density function theory (DFT) and the empirical pseudo-potential approach (EPM) with the virtual crystal approximation (VCA) have been used. The outcomes are expected to be used in optoelectronic applications and in understanding the mechanical properties of AlxIn1-xPySbzAs1-y-z alloy.

Mechanical and lattice vibrational investigations of nanostructured AlxIn1-xPySbzAs1-y-z alloys

The compositional dependence of the polarities, elastic constants, elastic moduli, Poisson's ratio, and linear compressibility has been computed for zinc blende AlxIn1-xPySbzAs1-y-z alloys with composition y ranging from 0 to 1. Also, the compositional influence of the bond-stretching force constant, bond-bending force constant, internal strain parameter, Cauchy ratio, effective charge, the Born ratio, anisotropy factor, and sound velocity has been determined. The experimental data and the studied properties for the novel studied alloy lattice matched to the InP substrate show a good level of agreement. The empirical pseudo-potential approach and the virtual crystal approximation have been employed in this work. The obtained results are predicted to help understand the elastic characteristics of AlxIn1-xPySbzAs1-y-z and for applications in optoelectronics.

Lattice dynamic and mechanical properties of GaxIn1-xPySbzAs1-y-z alloy lattice-matched to GaSb substrate

The local empirical pseudo-potential technique (EPM) modified with virtual crystal approximation (VCA) has been used to study the mechanical and vibrational properties of GaxIn1-xPySbzAs1-y-z lattice-matched to GaSb substrate. The material parameters considered are the elastic constants, the elastic moduli, bond-stretching (α), bond-bending (β) force constants, internal strain parameter (ζ), sound speed, phonon frequencies, and Deby temperature. The variation of the studied features with the compositional parameters is properly taken into account in the calculations. The data that is accessible in the literature and our estimated results agree well. To our knowledge, this is the first quantitative theoretical investigation on GaxIn1-xPySbzAs1-y-z quinternary alloys lattice-matched to GaSb compound of such properties and still awaits experimental confirmations. The results of this work seem likely to be serving as a useful reference.

Theoretical investigation of phonon modes related to first Brillouin zone centre and properties of double perovskites Ba2MWO6 (M=Mg, Zn, Cd)

In this research work, we investigate phonon modes related to the first Brillouin zone centre of double perovskites Ba2MgWO6, Ba2ZnWO6, and Ba2CdWO6. Besides, Debye temperature, elastic constants, and elastic properties are also evaluated. These investigations are carried out by employing a theoretical model based on the six parameters bond-bending force constant. From our calculations, we found the strength of the first-neighbor interaction is higher as compared to the second and third neighbor's interatomic interactions. Our computed results corresponding to Young, Bulk, and Shear moduli and Debye temperature are found in a sequence Ba2CdWO6>Ba2ZnWO6>Ba2MgWO6. Moreover, all the examined double perovskite compounds reveal their ductile and elastically anisotropic nature. Our predicted results for frequencies of zone-centre phonons and elastic constants also show nice agreement with previously reported results.

Electronic, optical, and mechanical properties of AlxIn1−xP alloys under temperature and pressure

In this work, the optoelectronic and mechanical properties of AlxIn1−xP combinations in the zinc-blende structure were studied for different Al concentrations. The energy band gaps left( {{text{E}}_{{text{g}}}^{{text{L}}} ,,{text{E}}_{{text{g}}}^{Gamma } ,,{text{E}}_{{text{g}}}^{{text{X}}} } right), refractive index (n), high frequency and static dielectric constants (ɛ∞, ɛo), elastic parameters (C11, C12, C44) were investigated. Other mechanical properties such as bulk (Bu), shear (Cs), Young’s (Y0) moduli, Poisson ratio (σ), linear compressibility (C_{o} ), Cauchy (C_{a} ) ratio, isotropy factor (A), bond stretching parameter (alpha ,), bond-bending force parameter (beta ,), internal-strain parameter (xi ), and the transverse effective charge (e_{T}^{*} ) were calculated. Also, the temperature and pressure dependences of these properties were studied. Our estimations were made with the empirical pseudo-potential method combined with the virtual crystal approximation incorporated the compositional disorder impact. There was a reasonable agreement between our determined outcomes and the accessible experimental values for the binary materials AlP and InP which give help for the consequences of the ternary combinations.

Impact of Substrates on the Electronic and Mechanical Properties of AlxIn1\u2212xPySb1\u2212y Alloys

The compositional dependence of electronic and mechanical properties of a AlxIn1−xPySb1−y quaternary alloy in zinc-blende structure lattice-matched to GaSb, InAs, and InP substrates is studied. The calculations are done based on the empirical pseudopotential method modified with virtual crystal approximation. Our calculations are obtained for the energy band gaps, elastic constants, elastic moduli, bond stretching, bond bending forces, and internal strain parameter. The material system of interest is found to be a direct semiconductor within a small range of Al concentrations about 0–0.07 and an indirect one outside this region. The Debye temperature and the Fröhlich coupling constant have been determined at different values of composition lattice-matched to different substrates. The phonon frequencies and the sound velocity for different substrates at various compositions have been studied. There is a good agreement between our results and the experimental data for its constituent binary compounds, AlP, AlSb, InP, InSb, and ternary alloys, InPSb, AlPSb, which supports the calculated results of the studied AlxIn1−xPySb1−y quaternary alloy. The studied properties for the considered alloy may be helpful for the fabrication of optoelectronic devices.

Effect of hydrostatic compression on physical properties of Li2TmSi3 (Tm = Ir, Pt, Rh, Os) with ground-state optical features

Using density functional theory (DFT) the first-principles calculations are employed to systematically investigate the effect of hydrostatic compression on the structural, elastic, electronic, thermal and thermodynamic properties of ternary silicides Li2TmSi3 (Tm = Ir, Pt, Rh, Os) with the ground-state optical features. The gradual decrease of bond length, unit cell volume and a smooth change of c/a with pressure deny the possibility of pressure induced phase transition up to 50 GPa. All the compounds studied here are mechanically stable within the considered pressure range. The constants C11, C12, C13 and C33 exhibit an almost linear increase trend with increase of pressure, while C44 shows anomalous behavior. The bond-stretching and bond-bending force constants are calculated based on the data of elastic constants and their pressure dependent behavior are discussed. Hydrostatic pressure enhances the inherent elastic anisotropy of Li2TmSi3. The ternary silicides studied here cannot be easily compressed under uniaxial stress. The atomic bonds between the nearest neighbors along [001] direction are stronger than those along [100] direction in the whole range of pressure. All ternary silicides except Li2PtSi3 are brittle in nature at ambient pressure. Under elevated pressure all studied compounds show brittle to ductile transition except Li2PtSi3 that exhibits brittle nature under 10 GPa. The shear modulus of Li2OsSi3 shows anomalous change under pressure, which may be attributed from its anomalous change of θD. The higher melting point of all silicides implies that they might have possible uses in harsh environments. The TDOS at EF in Li2TmSi3 decreases almost linearly with pressure. Pressure and temperature dependent thermodynamic properties and ground-state optical functions are described with implications, which may be supportive for further investigation of these compounds through experiments and theories.

Topological Constraint Theory Analysis of Rigidity Transition in Highly Coordinate Amorphous Hydrogenated Boron Carbide

Topological constraint theory (TCT) has revealed itself to be a powerful tool in interpreting the behaviors of amorphous solids. The theory predicts a transition between a ‘rigid’ overconstrained network and a ‘floppy’ underconstrained network as a function of connectivity or average coordination number, . The predicted results have been shown experimentally for various glassy materials, the majority of these being based on four-fold-coordinate networks such as chalcogenide and oxide glasses. Here, we demonstrate the broader applicability of topological constraint theory to uniquely coordinated amorphous hydrogenated boron carbide (a-BC:H), based on six-fold-coordinate boron atoms arranged into partially hydrogenated interconnected twelve-vertex icosahedra. We have produced a substantial set of plasma-enhanced chemical vapor deposited a-BC:H films with a large range of densities and network coordination, and demonstrate a clear threshold in Young’s modulus as a function of , ascribed to a rigidity transition. We investigate constraint counting strategies in this material and show that by treating icosahedra as ‘superatoms,’ a rigidity transition is observed within the range of the theoretically predicted c value of 2.4 for covalent solids with bond-stretching and bond-bending forces. This experimental data set for a-BC:H is unique in that it represents a uniform change in connectivity with and demonstrates a distinct rigidity transition with data points both above and below the transition threshold. Finally, we discuss how TCT can be applied to explain and optimize mechanical and dielectric properties in a-BC:H and related materials in the context of microelectronics applications.

First Brillouin zone-centre phonon frequencies and elastic stiffness of the Ln2Hf2O7 (Ln = La, Nd, Sm and Eu) pyrochlore

First Brillouin zone-centre phonon frequencies, elastic stiffness and mechanical properties of the Ln2Hf2O7 [Ln: La, Nd, Sm and Eu] pyrochlore structure were predicted by using an eight parameter bond-bending force constant model. One of the preliminary results of our study is that all the examined compounds are mechanically stable, and the elastic stiffness constants, and bulk and shear moduli decrease in the following sequence: La2Hf2O7→Nd2Hf2O7→Sm2Hf2O7→Eu2Hf2O7. The Poisson’s ratio reveals that the interatomic bonding of the studied compounds has an ionic character and their ionicity decreases when one moves from La to Eu. The elastic properties are anisotropic and the anisotropy increases from La to Eu. The Raman and infrared active and inactive modes of the studied materials were calculated. Our findings are in good accordance with the related available data.

Mechanical properties of AlPxSb1-x semiconductor alloys under the effect of temperature and pressure

Using the empirical pseudo-potential method (EPM) combined with the virtual crystal approximation (VCA) included the compositional disorder effect, some of optoelectronic and mechanical properties of AlPxSb1-x ternary alloys under the effect of pressure and temperature have been studied. Our results for the energy band gaps, refractive index, dielectric constants, elastic constants and some related parameters like elastic moduli, Poisson's ratio, bond stretching and bond bending force constants, internal strain parameter, linear compressibility, Cauchy ratio and anisotropy factor are successfully calculated for different values of temperature and pressure. A good agreement is noticed between our results and the available experimental and theoretical published data.

Influence of composition, temperature and pressure on the optoelectronic and mechanical properties of InPxSb1-x alloys

A detailed study of the effect of composition, temperature and pressure on the mechanical and optoelectronic properties of InPxSb1-x alloys has been reported. The calculations have been done using pseudo-potential method (EPM) within the improved virtual crystal approximation (VCA), where the compositional disorder effect is taken into account. Our results for the elastic constants, elastic moduli, Poisson's ratio, bond stretching force constant, bond bending force constant, internal strain parameter, linear compressibility, Cauchy ratio, and anisotropy factor are successfully calculated and compared with the available published data.

Vibrational and elastic properties of silicate spinels A2SiO4 (A = Mg, Fe, Ni, and Co)

A six-parameter bond-bending force constant model is used to calculate the zone-center (Γ = 0) Raman and infrared phonon mode frequencies, elastic constants and related properties, the Debye temperatures, and sound velocities along high-symmetry directions for A2SiO4 (A = Mg, Fe, Ni, and Co) spinels. The main outcomes of the calculations are that the interactions between Si and O atoms (first-neighbor interaction) are stronger than those between A and Oatoms (A = Mg, Fe, Ni, and Co) (second-neighbor interaction). The elastic constants C11, C12, and C44 decrease in the order Mg > Fe > Ni > Co. The calculated bulk modulus, Poisson's ratio, and anisotropy decrease in the sequence Fe2SiO4 → Ni2SiO4 → Co2SiO4 → Mg2SiO4. On comparison, we find overall good agreement with the available experimental and previously calculated data.

Vibrational and elastic properties of Ln2Sn2O7 (Ln = La, Sm, Gd, Dy, Ho, Er, Yb, or Lu)

In this study, an eight-parameter bond-bending force constant model was used to calculate the zone center phonon frequencies, elastic constants, and related properties of the stannate compounds Ln2Sn2O7 (Ln = La, Sm, Gd, Dy, Ho, Er, Yb, or Lu) with a pyrochlore structure. We found that the SnO bond strengths dominate the Ln-O and OO bonds. We also found that all of the materials are ductile and anisotropic in nature. The anisotropic nature of the compounds increases in the order of: La2Sn2O7 < Sm2Sn2O7 < Gd2Sn2O7 < Dy2Sn2O7 < Ho2Sn2O7 < Er2Sn2O7 < Yb2Sn2O7 < Lu2Sn2O7.

Vibrational, mechanical and thermodynamical properties of RE2Ti2O7 (RE = Sm, Gd, Dy, Ho, Er and Yb) pyrochlores

Vibrational, mechanical, thermodynamical properties and thermal conductivities of RE2Ti2O7 (RE = Sm, Gd, Dy, Ho, Er and Yb) pyrochlores have been calculated using a proposed eight-parameter bond-bending force constant model. The main outcome of present calculation is that the first neighbor interaction (Ti–O) is stronger than the second neighbor interactions (RE–O). This means that the bonding between Ti and O is more ionic than the one between RE and O. It is also found that the bond strength of RE–O and the bulk modulus decrease in the sequence Sm [Formula: see text] Gd [Formula: see text] Dy [Formula: see text] Ho [Formula: see text] Er [Formula: see text] Yb. The bulk moduli and Young’s moduli of RE2Ti2O7 also decrease when RE changes from Sm to Yb.

Electronic, optical, and mechanical properties of BN, AlN, and InN with zinc-blende structure under pressure

In this work, the electronic, optical, and mechanical properties of BN, AlN, and InN under the action of pressure are calculated. For each of these compounds, the energy band structure, band gaps , refractive index (n), dielectric constants (), elastic constants (), and relevant parameters such as bulk (), shear (), and Young’s () moduli are studied, and other important parameters such as bond-stretching (α), bond-bending (β) force constant, internal-strain parameter (ζ), effective charges (), anisotropy factor (), Poisson’s ratio (), Cauchy ratio (), the ductility index (), and linear compressibility () are also calculated. The effects of pressure on all studied properties are investigated. Our results are in good agreement with the available experimental and theoretical data for BN, AlN, and InN.

Inter atomic force constants of binary and ternary tetrahedral semiconductors

In this paper, we present the expressions relating the inter atomic force constants like as bond-stretching force constant (α in N/m) and bond-bending force constant (β in N/m) for the binary (zinc blende structure) and ternary (chalcopyrite structure) semiconductors with the product of ionic charges (PIC) and crystal ionicity (fi). Interatomic force constants of these compounds exhibit a linear relationship; when plot a graph between Interatomic force constants and the nearest neighbor distance d (A) with crystal ionicity (fi), but fall on different straight lines according to the product of ionic charges of these compounds. A fairly good agreement has been found between the observed and calculated values of the α and β for binary and ternary tetrahedral semiconductors.

Elasticity of randomly diluted honeycomb and diamond lattices with bending forces

We use numerical simulations and an effective-medium theory to study the rigidity percolation transition of the honeycomb and diamond lattices when weak bond-bending forces are included. We use a rotationally invariant bond-bending potential, which, in contrast to the Keating potential, does not involve any stretching. As a result, the bulk modulus does not depend on the bending stiffness κ. We obtain scaling functions for the behavior of some elastic moduli in the limits of small , and small , where is an occupation probability of each bond, and is the critical probability at which rigidity percolation occurs. We find good quantitative agreement between effective-medium theory and simulations for both lattices for close to one.

Lattice Dynamical Calculations for Inverse Spinel Compounds

Lattice dynamical calculations have been performed for inverse spinel structure compounds MIn2S4 (M = Mn and Co) using the proposed six parameter bond-bending force constant model. In this model, the short-range force constant is calculated by using the Taylor expansion of the potential energy in the harmonic approximation. This model is applied to study the zone-centre (Γ = 0) phonon frequencies of inverse spinels MIn2S4 (M = Mn and Co). The signi cant outcome of the present work is that the second neighbor interactions (octahedral bonding) are stronger than the rst neighbor interactions (tetrahedral bonding). The zone-center phonon frequencies, calculated using these parameters, are found to be in very good agreement with the observed results.

Structural properties of binary semiconductors

Using the plasma oscillations theory of solids, 2 empirical relations have been proposed for the calculation of the structural properties such as bond-stretching central force constant (α) and bond-bending non-central force constant (β) for II-VI and III-V group binary semiconductors. We find that α =D (N›ωp) 2 and β = S (N›ωp) 2, where D and S are constants. The numerical values of D and S are respectively, 0.151 and 0.016 for II-VI and 0.177 and 0.031 for III-V group binary semiconductors. The structural properties of binary semiconductors exhibit a linear relationship when plotted on a log-log scale against the plasmon energy N›ωp (in eV), which lies on the straight lines. We have applied the proposed empirical relations on these binary semiconductors and found a better agreement with the experimental data as compared to the values evaluated by earlier researchers. Key words: Plasmon energy, structural properties, III-V and II-VI Semiconductors.